Question

The sequence of communities of primary succession in water is:
A. Phytoplankton, sedges, free-floating hydrophytes, rooted hydrophytes, grasses and trees.
B. Phytoplankton, free-floating hydrophytes, rooted hydrophytes, sedges, grasses and trees.
C. Free-floating hydrophytes, sedges, phytoplankton, rooted hydrophytes, grasses and trees.
D. Phytoplankton, rooted submerged hydrophytes, floating hydrophytes, reed swamp, sedges, meadow and trees

Answer 1

Hint: The plant succession which occurs in water is known as hydrosere. It leads to the conversion of the water body and the communities within it to land communities. The edges of the water body consist of rooted species, submerged species, which are found below and on the open water zone planktons and floating species are present.

Complete answer:
The sequence of communities in the primary succession of water are:
1)Phytoplankton stage- The phytoplanktons, algae are the primary colonizers in the initial stages. They settle down to the bottom of the water after death and decompose to form humus and silt.

2)Submerged stage- The submerged rooted plants get established as the water becomes shallower. This leads to accumulation of organic and inorganic matter.

3)Floating stage- The plants are rooted with the leaves floating on the surface. These floating leaves make the environment unfit for the submerged species which die and decay and form mud.

4)Reed swamp stage- The water is further suitable for the emergent plants like reed grasses which form marsh or swamp. These plants bind the mud and produce litter which gets converted into marshy land.

5)Sedge-meadow stage- As the water surface gets covered by vegetation, the species like Gramineae, Juncus establish themselves. This further binds the soil. This habitat becomes suitable for the herbs to grow.

6)Woodland stage-The soil gets dry and becomes suitable for development of wet woodland. The shrubs, trees grow in this environment.

7)Climax forest- It can be forest or grassland depending on the grassland.

Hence, the correct answer is option (D)

Note: The succession from the aquatic habitat to climax woodland takes a long time, even centuries or millennium. The few intermediate stages are short lived whereas some stages are long lasting. The time required depends on the amount or silt or humus present in the habitat.